A differential output stage for electronic equipment generally includes a transformer enabling a differential output voltage to be obtained which is independent of connection conditions to the output terminals of the equipment.
The main problem posed by such a transformer, particularly in audiofrequency equipment, is its size, with this problem being aggravated by the fact that its characteristics concerning pass band, variation in output level with load, and harmonic distortion all improve with increasing bulk.
Differential output stages for electronic equipment, and in particular audiofrequency equipment, are also known which do not include transformers. Unlike those including transformers, they are compact, but they suffer from the drawback that the output level depends on the connection made. For example, if one of the output terminals is grounded, then since each of the output terminals contributes one-half to the differential output voltage, the differential output voltage is divided by two.
An object of the present invention is to provide a differential output stage for electronic equipment which does not include a transformer but which nevertheless makes it possible to obtain the same differential output voltage regardless of the connection conditions to the output terminals: terminal connected to ground, terminals open circuit, terminals loaded.
Another object of the present invention is to provide a differential output stage for audiofrequency electronic equipment making it possible, in the event of an output terminal being grounded, to avoid possible distortion in the differential output voltage.